The invention relates generally to electrical machines and, in particular, to a system and method of monitoring health of electrical machines.
In general, an electrical machine such as power generator or motor is routinely monitored for proper maintenance and high efficiency during operation. One of the few aspects of monitoring health of the electrical machine is inspecting stator bar windings to ensure the windings are motionless during the operation. Typically, an electrical machine includes a wedge system to induce a radial retaining force to a stator to facilitate reducing movement of the stator bar windings within a stator slot. Such a wedge system may also include ripple springs embedded in the stator winding assembly. The ripple springs are generally in a state of compression to keep the windings from moving. In case, the wedge system becomes loose, the amount of retaining force is reduced such that the stator bar windings may move during operation. Over time, the relative motion of the stator bar windings causes damage to the insulation surrounding the stator bar wedges and a potential stator bar winding failure can occur. This may result in electrical shorts to ground, thereby, diminishing the efficiency of the machine and further decreasing the mean time between failures of the electrical machines. Therefore, it is desired that the stator bar winding movement or the wedge tightness be continuously monitored using sensors. However, the sensors used for monitoring have the tendency to drift with time due to various operating parameter and hence are unstable over a period of time, resulting in inaccurate monitoring of health of electrical machines. Additionally since re-wedging or rewinding of electrical machines may be infrequent, the sensor drift over time may limit the usefulness of the monitoring to short periods of time compared to the expected life of the electrical machine.
Therefore, to assess the condition of the electrical machine, there is a need for an efficient monitoring system that easily and accurately monitors the health of the machine.